Normally closed microelectromechanical switches (mems), methods of manufacture and design structures

ABSTRACT

Normally closed (shut) micro-electro-mechanical switches (MEMS), methods of manufacture and design structures are provided. A method of forming a micro-electrical-mechanical structure (MEMS), includes forming a plurality of electrodes on a substrate, forming a beam structure in electrical contact with a first of the electrodes, and bending the beam structure with a thermal process. The method further includes forming a cantilevered electrode extending over an end of the bent beam structure, and returning the beam structure to its original position, which will contact the cantilevered electrode in a normally closed position.

FIELD OF THE INVENTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to normally closed (shut)micro-electro-mechanical switches (MEMS), methods of manufacture anddesign structures.

BACKGROUND

Integrated circuit switches used in integrated circuits can be formedfrom solid state structures (e.g., transistors) or passive wires (MEMS).MEMS switches are typically employed because of their almost idealisolation, which is a critical requirement for wireless radioapplications where they are used for mode switching of power amplifiers(PAs) and their low insertion loss (e.g., resistance) at frequencies of10 GHz and higher. MEMS switches can be used in a variety ofapplications, primarily analog and mixed signal applications. One suchexample is cellular telephone chips containing a power amplifier (PA)and circuitry tuned for each broadcast mode. Integrated switches on thechip would connect the PA to the appropriate circuitry so that one PAper mode is not required.

Depending on the particular application and engineering criteria, MEMSstructures can come in many different forms. For example, MEMS can berealized in the form of a cantilever beam structure. In the cantileverstructure, a cantilever arm (suspended electrode with one end fixed) ispulled toward a fixed electrode by application of an actuation voltage.The voltage required to pull the suspended electrode to the fixedelectrode by electrostatic force is called pull-in voltage, which isdependent on several parameters including the length of the suspendedelectrode, spacing or gap between the suspended and fixed electrodes,and spring constant of the suspended electrode, which is a function ofthe materials and their thickness. Alternatively, the MEMS beam could bea bridge structure, where both ends are fixed.

However, as semiconductors become smaller, due to scaling, severalissues can arise in the MEMS. For instance, silicon scaling leads tosmaller ratios of power required to turn on and turn off semiconductordevices, which results in power being transferred through semiconductordevices when power should not be transferred, e.g., when thesemiconductor devices are turned off. This is evidenced by off currentsin semiconductor devices being measurable. Moreover, silicon scalingmakes it more difficult and more costly to radiation hardensemiconductor devices on chips, especially when there are many devicesand each of the devices are extremely small.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

SUMMARY

In a first aspect of the invention, a method of forming amicro-electrical-mechanical structure (MEMS), includes forming aplurality of electrodes on a substrate, and forming a beam structure inelectrical contact with a first of the electrodes; bending the beamstructure with a thermal process. The method further includes forming acantilevered electrode extending over an end of the bent beam structure,and returning the beam structure to its original position, which willcontact the cantilevered electrode in a normally closed position.

In another aspect of the invention, a structure includes a beamstructure includes a first end hinged on a first electrode and inelectrical contact with a second electrode, in its natural state whennot actuated.

In yet another aspect of the invention, a method in a computer-aideddesign system for generating a functional design model of amicromechanical switch, includes generating a functional representationof a beam structure comprising a first end hinged on a first electrodeand in electrical contact with a second electrode, in its natural statewhen not actuated.

In another aspect of the invention, a design structure tangibly embodiedin a machine readable storage medium for designing, manufacturing, ortesting an integrated circuit is provided. The design structurecomprises the structures of the present invention. In furtherembodiments, a hardware description language (HDL) design structureencoded on a machine-readable data storage medium comprises elementsthat when processed in a computer-aided design system generates amachine-executable representation of a normally closedmicro-electro-mechanical switch (MEMS), which comprises the structuresof the present invention. In still further embodiments, a method in acomputer-aided design system is provided for generating a functionaldesign model of the normally closed MEMS. The method comprisesgenerating a functional representation of the structural elements of thenormally closed MEMS.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIGS. 1-6 show fabrication steps and respective structures in accordancewith aspects of the invention;

FIG. 7 shows an exemplary circuit diagram of the structure shown in FIG.6 in accordance with aspects of the invention;

FIG. 8 shows an exemplary complementary MEMS-based structure andrespective processing steps in accordance with aspects of the invention;

FIG. 9 shows an exemplary circuit diagram of the complementaryMEMS-based structure in FIG. 8 in accordance with aspects of theinvention; and

FIG. 10 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test.

DETAILED DESCRIPTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to normally closed (shut)micro-electro-mechanical switches (MEMS), methods of manufacture anddesign structures. More specifically, the present invention is directedto normally closed MEMS structures, which include a hinged beamstructure fabricated in a closed position. In embodiments, the beamstructure of the normally closed MEMS is, in operation, normally inelectrical contact with an electrode. Upon actuation of a controlelectrode, the cantilever beam structure will be separated from theelectrode, thereby opening the switch.

In embodiments, the beam structure of the normally closed MEMS isfabricated with a stress film. In embodiments, the stress film has acoefficient of thermal expansion (CTE) different from that of the beamstructure of the normally closed MEMS. The stress film provides stresson the beam structure of the normally closed MEMS during manufacturingwhich, in turn, bows or bends the cantilever beam structure of thenormally closed MEMS, e.g., upon application of heat. In this position,an upper electrode can be fabricated, such that it will not be incontact with the beam structure. In embodiments, upon removal of thestress film, the beam structure of the normally closed MEMS returns toits natural position, e.g., in electrical contact with the electrode. Inthis way, the beam structure of the normally closed MEMS remains incontact with the electrode, and upon application of voltage by a controlelectrode, will be separated therefrom (e.g., resulting in an opencircuit). In embodiments, the normally closed beam structure can beassembled into a complementary MEMS based structure, and can beimplemented as an inverter, NAND, SRAM cell and other standard CMOSlogic gate structures.

Advantageously, the structures of the present invention can completelyturn off at least one device through physically and electricallydisconnecting, e.g., separating, the beam structure from an outputelectrode. Further, the structures of the present invention may preventlarge off currents leaking through semiconductor devices since aconduction mechanism (e.g., beam structure) is tunneling through air.The MEMS devices of the present invention are also undisturbed bydynamic switching and power variations from such switching.

FIG. 1 shows a structure and respective processes for fabricating inaccordance with aspects of the invention. The structure includes asubstrate 10 (e.g., a wafer body) that, in embodiments, can include anybulk substrate, such as silicon, copper, aluminum, etc. Metal contacts15, 20, and 25 are formed in trenches of the substrate 10. Inembodiments, the metal contacts 15, 20, 25 may be formed through forexample, by conventional lithography, etching and deposition processes.For example, a resist can be formed on the substrate 10 and exposed tolight to form openings (patterns). A reactive ion etching (RIE), forexample, may then be used to form trenches in the substrate 10. Thetrenches can be filled with conductive materials such as, for example,copper, tungsten, and/or aluminum, to form the metal contacts 15, 20,25. The surface of the structure can be planarized using a chemicalmechanical polishing (CMP).

Still referring to FIG. 1, conductive pads 30, 35, and 40 are formed onthe surface of the structure, in physical and electrical contact withthe contacts 15, 20, and 25, respectively. In embodiments, theconductive pads 30, 35, 40 can be formed by any conventional processessuch as, for example, a damascene process or blanket metal depositionand RIE process. In embodiments, the conductive pads 30, 35, 40 can beany conductive material such as, for example, aluminum, copper and/ortungsten.

In a damascene process, an insulator film, e.g., oxide, may be formed onthe surface of the structure, which is then polished, e.g., via a CMP.Trenches can then be etched into the film using conventional lithographyand etching processes. The trenches are then filled with conductivematerial, such as copper, tungsten, and/or aluminum. The surface of thestructure is then planarized using a CMP. A portion or all of the filmmay be removed; although, in embodiments, some or all of the film mayremain on the surface for subsequent processing steps.

In an alternative process, the conductive pads 30, 35, 40 can be formedby a blanket deposition and RIE process. For example, conductivematerial can be blanket-deposited on the structure and etched usingconventional RIE processes. More specifically, the conductive materialcan be blanket deposited using a sputtering or vapor deposition process.A resist can be formed on the conductive material, and exposed to lightto form openings. The exposed conductive material can then be removedusing a RIE process, through the openings, to form the conductive pads,30, 35, 40. The resist can then be removed using conventional ashingprocesses.

Still referring to FIG. 1, in one illustrative, non-limiting example,the conductive pads 30, 35, 40 can have a thickness within a rangeconventional to one of ordinary skill in the art. As should beunderstood by those of ordinary skill in the art, each of the conductivepads 30, 35, 40 comprises a respective portion of an input electrode, acontrol electrode, and an output electrode, respectively.

In FIG. 2, conductive pads 45 and 50 are formed on the conductive pads30 and 40, respectively, to form raised electrodes, e.g., input andoutput electrode or ground. The conductive pads 45 and 50 are inphysical and electrical contact with the conductive pads 30 and 40,respectively. In embodiments, the conductive pads 45 and 50 can beformed through any conventional processes including, for example,conventional damascene or blanket metal deposition and RIE process. Forexample, in a damascene process, an insulator film, e.g., oxide, may beformed over the exposed portions of the substrate 10 (or, inembodiments, any oxide film remaining in previous processing steps) andthe conductive pads 30, 35 and 40. In embodiments, the film can then bepolished, e.g., via a CMP. The film then undergoes an etching process toform trenches aligned with the conductive pads 30 and 40. The trenchesare filled with conductive materials, such as copper, tungsten, and/oraluminum, and thereafter planarized to form conductive pads 45 and 50.In embodiments, the conductive pads 35, 45 and 50 can be masked, so thatthe film can be removed, while protecting the conductive pads. Inembodiments, a portion or all of the film can remain on the surface forsubsequent processes.

Still referring to FIG. 2, in alternative embodiments, the conductivepads 45 and 50 can be formed using a conventional blanket deposition andRIE process. In this scenario, conductive material may beblanket-deposited on the structure, e.g., substrate 10, any remainingfilm, as well as on the conductive pads 30, 35 and 40, usingconventional deposition processes. The conductive material is thenmasked over the conductive pads 30 and 40, and the remaining, exposedportions of the conductive material are removed, e.g., etched, using aRIE process. The mask is then removed, leaving the conductive pads 45and 50, in electrical contact and aligned with the conductive pads 30and 40. In embodiments, any residual film from any previous damasceneprocess may also be removed; although, the present invention alsocontemplates the residual oxide remaining on the surface for subsequentprocessing steps.

Still referring to FIG. 2, in one illustrative, non-limiting example,the conductive pads 45, 50 can include a thickness within a rangeconventional to one of ordinary skill in the art. In embodiments, theconductive pads 45 and 50 form portions of the input electrode and theoutput electrode, respectively, of the MEMS device. In this way, theinput and output electrodes are raised structures with respect to acontrol electrode, e.g., the conductive pad 35 and the metal contact 20.

In FIG. 3, an insulator film 55 is formed on the structure, e.g., on theconductive pads 35, 45, and 50 and any exposed portions of theunderlying substrate 10. In embodiments, the insulator film 55 can be anoxide or other insulator film used during previous damascene processes,which will reduce overall manufacturing time and costs. In embodiments,the insulator film 55 can alternatively be formed through anyconventional oxidation process and/or a chemical vapor deposition (CVD)process. After formation, the insulator film 55 may be polished (e.g.,via a CMP) to a surface level of the conductive pads 45 and 50, e.g., toexpose a surface of the conductive pads 45 and 50.

Still referring to FIG. 3, a beam structure 60 and a conductive pad 65are formed on the surface of the insulator film 55. In embodiments, thebeam structure 60 is in physical and electrical contact with theconductive pads 45; whereas, the conductive pad 65 is in physical andelectrical contact with the conductive pad 50. In embodiments, the beamstructure 60 can be any type of cantilever beam such as, for example, arotating gear, and/or any other type of beam known in the art. Thecantilever beam structure 60 and the conductive pad 65 may includeconductive metal materials, such as copper, tungsten, and/or aluminum.

The beam structure 60 and the conductive pad 65 can be formed using adamascene process or metal deposition and RIE processes, known to thoseof skill in the art. For example, in a damascene process, an insulatorfilm 55, e.g., oxide, is formed on the structure and polished, e.g., viaa CMP, to expose the surfaces of the conductive pads 45 and 50. Inembodiments, the insulator film 55 can be a film formed during previousdamascene processes. A second insulator film is then formed on theinsulator film 55, which is then subjected to a conventional patterningprocess to form trenches. A conductive material then fills the trenches,e.g., copper, tungsten, and/or aluminum. The additional layer ofinsulator film can then be removed, leaving behind the beam structure 60and the conductive pad 65.

In an alternative embodiment, a blanket deposition and RIE process maybe used to form the cantilever beam structure 60 and the conductive pad65. In this alternative approach, conductive material can beblanket-deposited on the insulator film 55 and patterned to form thecantilever beam structure 60 and the conductive pad 65. The depositionof the conductive material may be a vapor deposition process or asputtering process, for example. The patterning can be performed usingconventional lithographic and etching (RIE) processes. In eitherapproach, the insulator film (which may include the film 55) can beselectively removed or left intact for subsequent processes.

In one illustrative, non-limiting example, the beam structure 60 and theconductive pad 65 can have a thickness within a range conventional toone of ordinary skill in the art. Also, as shown in FIG, 3, the beamstructure 60 is hinged mounted onto the input electrode, e.g., metalcontacts 15 and pads 30, 40. This will allow the beam structure 60 toeither contact or separate from an output electrode.

In FIG. 4, a stress film 70 is formed on the cantilever beam structure60. In embodiments, the stress film 70 can include any material with acoefficient of thermal expansion (CTE) that is greater than a CTE of thebeam structure 60. For example, if the beam structure 60 includescopper, the stress film 70 may include a polymer, and be formed in athickness determined based on a ratio of the CTE between the beamstructure 60 and the stress film 70, and a desired angle of deflectionbetween the beam structure 60 and the stress film 70. In embodiments,the stress film 70 may include one or more of the following materialswith their respective CTE's (in parts per million (ppm) per degreeCelsius (° C.)):

TABLE 1 Material CTE (ppm/° C.) AlAs 4.9 AlP 4.5 Alumina 6-7 AsSb 4Copper 16.7 Cu/l/Cu 8.4 Cu/Mo/Cu 6 Cu/Mo—Cu/Cu  6-10 E-glass 54 Epoxy 55Fused Silica 0.55 Gallium Arsenide (GaAs) 6.86 GaP 4.5 GaSb 7.75Germanium (Ge) 5.8 InAs 4.52 InP 4.75 InSb 5.37 Invar 1.3 Kovar 5.9Molybdenum 7.0-7.1 Polymers  50-200 S-glass 16 Silicon 2.6 SiliconNitride (Si₃N₄) 3.2 Silicon resins  30-300 Tin-Lead Solder 27 Titanium9.5 Tungsten 5.7-8.3

In embodiments, the stress film 70 can be formed using conventionaldeposition processes. For example, in embodiments, a mask can be formedover the conductive pad 65, e.g., deposited on the structure andpatterned to remove portions aligned with the cantilever beam structure60. The stress film 70 can then be deposited in the openings of the maskto form the stress film on a surface of the cantilever beam structure60.

FIG. 5 shows several processing steps and a respective structure inaccordance with aspects of the invention. In particular, in FIG. 5, acantilevered conductive pad 75 is formed on the conductive pad 65 using,for example, a damascene process or blanket deposition and RIEprocesses. In either of these processes, the stress film 70 will imposea stress component on the beam structure 60 due to a CTE mismatch duringthe heating cycle of these processes, e.g., the CTE of the stress film70 being greater than the CTE of the cantilever beam structure 60,resulting in a downward bowing or bending of the beam structure 60. Thisensures that the beam structure 60 is not in contact with thecantilevered conductive pad 75 during fabrication processes, therebyensuring that the beam structure 60 will not stick to the cantileveredconductive pad 75. In embodiments, the cantilevered conductive pad 75will form the contact portion of the output electrode. In oneillustrative, non-limiting example, the cantilevered conductive pad 75can have a thickness and a length within ranges conventional to one ofordinary skill in the art.

To form the structure of FIG. 5, for example, the insulator film 55 orportions thereof underneath the beam structure 60 is removed by anyconventional removal processes. This allows the beam structure 60 tobend downwards (e.g., towards the conductive pad 35) during subsequentthermal processes. In the damascene process, a second insulator film isformed on the structure, e.g., beam structure 60 and conductive pad 65,which is patterned to form an opening for deposition of the conductivematerial comprising the cantilevered conductive pad 75. In embodiments,the conductive material is preferably different than the materialcomprising the beam structure 60 to prevent these components fromgrowing permanent bonds together if left in contact over time. Duringthe formation of the insulator film, e.g., oxide, the beam structure 60will bend downwards due to the CTE mismatch between the material of thebeam structure 60 and the stress film 70. Thereafter, the insulator filmcan be removed, leaving the cantilevered conductive pad 75. Inembodiments, the cantilevered conductive pad 75 extends beyond an end 60a of the beam structure 60. In this way, the cantilever beam structure60 and cantilevered conductive pad 75 can make electrical contact.

In the blanket deposition and RIE process, an insulator film is firstformed over the stress film 70 and other structures of the device, andplanarized to form a planar, flat surface, which exposes the conductivepad 65. The conductive material is then blanket deposited on theinsulator film and patterned to form the cantilevered conductive pad 75.Similar to the damascene process, the processes described in thisalternative process are performed at an increased temperature, whichwill bend the beam structure 60 downwards due to the CTE mismatchbetween the material of the beam structure 60 and the stress film 70. Inboth the damascene process and the blanket deposition and RIE processes,the stress film 70 is removed through a selective etching process, e.g.,a chemistry that is selective to the removal of the material comprisingthe stress film 70.

Still referring to FIG. 5, in embodiments, the beam structure 60 and thecantilevered conductive pad 75 can be composed of the same or similarconductive materials. In this case, a seed layer 80 can be formed on thestress film 70, in physical and electrical contact therewith. Inembodiments, the seed layer 80 would be formed between the stress film70 and the cantilevered conductive pad 75, where the conductive pad 75is formed over at least a portion of the stress film 70 and the beamstructure 60. The seed layer 80 can include metal materials, such astungsten and/or magnesium. The seed layer 80 prevents the conductivemetal materials of the beam structure 60 from migrating to theconductive metal materials of the conductive pad 75, and vice versa, andfrom growing permanent bonds together if left in contact over time.

FIG. 6 shows a final structure and respective process steps inaccordance with aspects of the invention. In this structure, the stressfilm 70 and the seed layer 80 are removed using conventional processes.As thus shown, upon the removal of the stress film 70, the beamstructure 60 bends back to its original position, now in contact withthe cantilevered conductive pad 75. As the cantilevered conductive pad75 and the beam structure 60 are normally in contact with each other,the device of the present invention is in a normally shut (closed)state.

FIG. 6 also shows an optional compressive film 90 formed on the beamstructure 60. In embodiments, after removal of the stress film 70, ifthe cantilevered conductive pad 75 is at a greater height than the beamstructure 60, e.g., separated therefrom so as to not be in contact, thecompressive film 90 can be formed on and in physical and electricalcontact with the beam structure 60. The compressive film 90 may increasethe height of the beam structure 60 such that the beam structure 60 canbe in electrical contact with the conductive pad 75. The compressivefilm 90 may include at least one of the materials in Table 1 shownabove, such that a material of the compressive film 90 has a differentCTE at room temperature than the CTE of the conductive pad 75. Thisprevents the beam structure 60 and the conductive pad 75 from growingpermanent bonds together if left in contact over time.

FIG. 7 shows an exemplary circuit diagram 100 of the final structure ofFIG. 6 in accordance with aspects of the invention. The circuit diagram100 includes an input electrode (“IN”), a control electrode (“CNTL”), anoutput electrode (“OUT”), and a device 105. In embodiments, the device105 can be a cantilever beam (as shown here), or other switch mechanismin the normally closed state. The device 105 may include arms connectedto ground. If the arms are connected to an integrated circuit powersupply pin (VDD), then the device would be a MEMS-based normally openswitch (NOS).

Still referring to FIG. 7, the device 105 is normally in the closedstate, connecting to both the input electrode and the output electrode.Accordingly, when the control electrode is not supplying a controlvoltage, then the device 105 connects the input electrode to the outputelectrode, e.g., shut. In this case, the device 105 may receive an inputvoltage supplied from the input electrode, which can be connected to avoltage source such as another circuit. The device 105 may then transferthe input voltage to the output electrode, which can be connected toanother circuit, for example. If the control electrode supplies acontrol voltage, then the device 105 will disconnect (separate) from theoutput electrode, e.g., be open. In this manner, the device 105 does nottransfer any voltage between the input electrode and the outputelectrode.

FIG. 8 shows an exemplary complementary MEMS -based structure 200 inaccordance with aspects of the invention. More specifically, thecomplementary MEMS-based structure 200 is an inverter, which includes aMEMS-based open device 205 and a MEMS-based closed device 210, formed ona substrate 215 using processes as described in FIGS. 1-6. Morespecifically, the MEMS-based closed device 210 is formed in the manneras described in FIGS. 1-6; whereas the MEMS -based open device 205 doesnot include the use of a compressive film or the cantilevered beamstructure, as an output electrode. Instead, the MEMS-based open device205 will contact with a lower level ground electrode 220.

In embodiments, the MEMS-based open device 205 can include a groundelectrode 220, an input electrode 225, an output electrode 230, and abeam structure 235A. The ground electrode 220 may be connected to groundand be built up to a first layer over the substrate 215. The inputelectrode 225 can be connected to a voltage source (e.g., anotherdevice) and be built up to a first layer over the substrate 215. Theoutput electrode 230 may be connected to another device and be built upto a third layer over the substrate 215. The beam structure 235A can bea cantilever beam (as shown here), a rotating gear, and/or any otherbeam structure known in the art that may be switched between differentstates. The beam structure 235A is a device hinged on the outputelectrode that either connects or disconnects the ground electrode 220and the output electrode 230, and is controlled by the input electrode225. At an initial state (e.g., when there is no static voltage at theinput electrode 225), the beam structure 235A is disconnected from theground electrode 220, or the MEMS-based open device 205 is normallyopen.

Still referring to FIG. 8, in embodiments, the MEMS-based closed device210 can include the output electrode 230, a beam structure 235B, aninput electrode 240, and an integrated circuit power supply pin (VDD)245. The VDD 245 may be connected to a power supply and be built up tothe second layer and the third layer over the substrate 215. The inputelectrode 240 can be connected to a voltage source (e.g., anotherdevice) and be built up to the first layer over the substrate 215. Theoutput electrode 230 may be connected to another device and be built upto the second layer and the third layer over the substrate 215. The beamstructure 235B can be a cantilever beam (as shown here), a rotatinggear, and/or any other beam structure known in the art that may beswitched between different states. The beam structure 235B may includearms connected to ground. The beam structure 235B is a device hinged onthe output electrode that either connects or disconnects the outputelectrode 230 and the VDD 245, and is controlled by the input electrode240. At an initial state (e.g., when there is no static voltage at theinput electrode 240), the beam structure 2358 connects the outputelectrode 230 and the VDD 245, or the MEMS-based closed device 210 isnormally shut.

FIG. 9 shows an exemplary circuit diagram 300 of the complementarystructure shown in FIG. 8. More specifically, the circuit diagram 300 isof the complementary MEMS-based structure 200 (e.g., the inverter) ofFIG. 8. The circuit diagram 300 includes a MEMS based open device 305and a MEMS based closed device 310, e.g., the MEMS based open device 205and the MEMS based closed device 210, respectively. The MEMS based opendevice 305 includes a ground electrode (“GND”), an input electrode(“IN”), an output electrode (“OUT”), and a beam structure 315A. The MEMSbased closed device 310 includes the output electrode, the inputelectrode, a VDD electrode (“VDD”), and a beam structure 315B. Inembodiments, each of the MEMS devices 315A, 315B can be a cantileverbeam (as shown here), a rotating gear, and/or any other beam structureknown in the art that may be switched between different states. Each ofthe beam structures 315A, 315B may include arms connected to ground.

Still referring to FIG. 9, the beam structure 315A is a device hinged onthe input or output electrode that either connects or disconnects theground electrode and the output electrode, while the beam structure 315Bis a device hinged on the output electrode that either connects ordisconnects the output electrode and the VDD electrode. The beamstructures 315A, 315B are controlled by the input electrode. Forexample, if the input electrode (which can be connected to a voltagesource such as another circuit) is not supplying an input voltage, thenthe beam structure 315A may be disconnected from the output electrode,or be open. Meanwhile, the beam structure 315B can be connected betweenthe output electrode and the VDD electrode, or be shut. In this case,the beam structure 315B may receive a VDD voltage supplied from the VDDelectrode, which can be connected to a power supply. The beam structure315B may then transfer the VDD voltage to the output electrode, whichcan be connected to another circuit, for example. If the input electrodeis supplying an input voltage, then the beam structure 315A may beconnected between the ground electrode and the output electrode, or beshut. On the other hand, the beam structure 315B can be disconnectedfrom the output electrode, or be open. In this manner, the beamstructure 315A may receive a ground (“GND”) voltage supplied from theground electrode, which can be connected to ground. The beam structure315A may then transfer the ground voltage to the output electrode. Thecircuit diagram 300 (e.g., the inverter) can be represented by thefollowing truth table:

TABLE 2 IN OUT 0 VDD 1 GNDwhere the VDD voltage and the GND voltage may be set to anypredetermined voltage level without impacting the switching performanceof the structure of the invention.

FIG. 10 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test. FIG. 10 shows a block diagram of anexemplary design flow 900 used for example, in semiconductor IC logicdesign, simulation, test, layout, and manufacture. Design flow 900includes processes, machines and/or mechanisms for processing designstructures or devices to generate logically or otherwise functionallyequivalent representations of the design structures and/or devicesdescribed above and shown in FIGS. 1-9. The design structures processedand/or generated by design flow 900 may be encoded on machine-readabletransmission or storage media to include data and/or instructions thatwhen executed or otherwise processed on a data processing systemgenerate a logically, structurally, mechanically, or otherwisefunctionally equivalent representation of hardware components, circuits,devices, or systems. Machines include, but are not limited to, anymachine used in an IC design process, such as designing, manufacturing,or simulating a circuit, component, device, or system. For example,machines may include: lithography machines, machines and/or equipmentfor generating masks (e.g. e-beam writers), computers or equipment forsimulating design structures, any apparatus used in the manufacturing ortest process, or any machines for programming functionally equivalentrepresentations of the design structures into any medium (e.g. a machinefor programming a programmable gate array).

Design flow 900 may vary depending on the type of representation beingdesigned. For example, a design flow 900 for building an applicationspecific IC (ASIC) may differ from a design flow 900 for designing astandard component or from a design flow 900 for instantiating thedesign into a programmable array, for example a programmable gate array(PGA) or a field programmable gate array (FPGA) offered by Altera® Inc.or Xilinx® Inc.

FIG. 10 illustrates multiple such design structures including an inputdesign structure 920 that is preferably processed by a design process910. Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may also or alternatively comprise data and/or programinstructions that when processed by design process 910, generate afunctional representation of the physical structure of a hardwaredevice. Whether representing functional and/or structural designfeatures, design structure 920 may be generated using electroniccomputer-aided design (ECAD) such as implemented by a coredeveloper/designer. When encoded on a machine-readable datatransmission, gate array, or storage medium, design structure 920 may beaccessed and processed by one or more hardware and/or software moduleswithin design process 910 to simulate or otherwise functionallyrepresent an electronic component, circuit, electronic or logic module,apparatus, device, or system such as those shown in FIGS. 1-9. As such,design structure 920 may comprise files or other data structuresincluding human and/or machine-readable source code, compiledstructures, and computer-executable code structures that when processedby a design or simulation data processing system, functionally simulateor otherwise represent circuits or other levels of hardware logicdesign. Such data structures may include hardware-description language(HDL) design entities or other data structures conforming to and/orcompatible with lower-level HDL design languages such as Verilog andVHDL, and/or higher level design languages such as C or C++.

Design process 910 preferably employs and incorporates hardware and/orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIGS. 1-9 to generate a netlist980 which may contain design structures such as design structure 920.Netlist 980 may comprise, for example, compiled or otherwise processeddata structures representing a list of wires, discrete components, logicgates, control circuits, I/O devices, models, etc. that describes theconnections to other elements and circuits in an integrated circuitdesign. Netlist 980 may be synthesized using an iterative process inwhich netlist 980 is resynthesized one or more times depending on designspecifications and parameters for the device. As with other designstructure types described herein, netlist 980 may be recorded on amachine-readable data storage medium or programmed into a programmablegate array. The medium may be a non-volatile storage medium such as amagnetic or optical disk drive, a programmable gate array, a compactflash, or other flash memory. Additionally, or in the alternative, themedium may be a system or cache memory, buffer space, or electrically oroptically conductive devices and materials on which data packets may betransmitted and intermediately stored via the Internet, or othernetworking suitable means.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including netlist980. Such data structure types may reside, for example, within libraryelements 930 and include a set of commonly used elements, circuits, anddevices, including models, layouts, and symbolic representations, for agiven manufacturing technology (e.g., different technology nodes, 32 nm,45 nm, 90 nm, etc.). The data structure types may further include designspecifications 940, characterization data 950, verification data 960,design rules 970, and test data files 985 which may include input testpatterns, output test results, and other testing information. Designprocess 910 may further include, for example, standard mechanical designprocesses such as stress analysis, thermal analysis, mechanical eventsimulation, process simulation for operations such as casting, molding,and die press forming, etc. One of ordinary skill in the art ofmechanical design can appreciate the extent of possible mechanicaldesign tools and applications used in design process 910 withoutdeviating from the scope and spirit of the invention. Design process 910may also include modules for performing standard circuit designprocesses such as timing analysis, verification, design rule checking,place and route operations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures along with any additional mechanical designor data (if applicable), to generate a second design structure 990.

Design structure 990 resides on a storage medium or programmable gatearray in a data format used for the exchange of data of mechanicaldevices and structures (e.g. information stored in a IGES, DXF,Parasolid XT, JT, DRG, or any other suitable format for storing orrendering such mechanical design structures). Similar to designstructure 920, design structure 990 preferably comprises one or morefiles, data structures, or other computer-encoded data or instructionsthat reside on transmission or data storage media and that whenprocessed by an ECAD system generate a logically or otherwisefunctionally equivalent form of one or more of the embodiments of theinvention shown in FIGS. 1-9. In one embodiment, design structure 990may comprise a compiled, executable HDL simulation model thatfunctionally simulates the devices shown in FIGS. 1-9.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.information stored in a GDSII (GDS2), GL1, OASIS, map files, or anyother suitable format for storing such design data structures). Designstructure 990 may comprise information such as, for example, symbolicdata, map files, test data files, design content files, manufacturingdata, layout parameters, wires, levels of metal, vias, shapes, data forrouting through the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIGS. 1-9. Design structure990 may then proceed to a stage 995 where, for example, design structure990: proceeds to tape-out, is released to manufacturing, is released toa mask house, is sent to another design house, is sent back to thecustomer, etc.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims, if applicable, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain theprincipals of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated. Accordingly, while the invention has beendescribed in terms of embodiments, those of skill in the art willrecognize that the invention can be practiced with modifications and inthe spirit and scope of the appended claims.

1. A method of forming a micro-electrical-mechanical structure (MEMS),comprising: forming a plurality of electrodes on a substrate; forming abeam structure in electrical contact with a first of the electrodes;bending the beam structure with a thermal process; forming acantilevered electrode extending over an end of the bent beam structure;and returning the beam structure to its original position, which willcontact the cantilevered electrode in a normally closed position.
 2. Themethod of claim 1, wherein the bending of the beam structure comprisesforming a stress film on the beam structure, and subjecting the beamstructure and the stress film through a thermal cycle.
 3. The method ofclaim 2, wherein the beam structure and the stress film have differentcoefficient of thermal expansion (CTE).
 4. The method of claim 2,wherein the stress film is removed after forming of the cantileveredelectrode, which returns the beam structure to its original position. 5.The method of claim 2, further comprising: forming a seed layer betweenthe stress film and the cantilevered electrode, the seed layercomprising a metal comprising at least one of tungsten and magnesium;and removing the stress film and the seed layer such that the beamstructure bends back up to its original position and its end contactsthe cantilevered electrode.
 6. The method of claim 1, wherein the beamstructure is formed from a first material and the cantilevered electrodeis formed from a second material, different from the first material. 7.The method of claim 1, wherein the forming of the plurality ofelectrodes comprises forming a first and second raised electrode portionin a plurality of metal deposition steps and a third electrode is formedin a single metal deposition step, on the substrate, wherein thecantilevered electrode is formed on the second raised portion.
 8. Themethod of claim 1, wherein the beam structure and the cantileveredelectrode are formed from a same material, and a film is placed on topof the stress film prior to the fabricating of the cantileveredelectrode.
 9. The method of claim 1, further comprising forming acompressive film on beam structure.
 10. The method of claim 1, whereinthe plurality of electrodes are formed by a damascene process.
 11. Themethod of claim 1, wherein the beam structure and the cantileveredelectrode are formed by a damascene process.
 12. The method of claim 1,wherein the beam structure is formed extending from one of theelectrodes, as a cantilever.
 13. The method of claim 1, wherein the beamstructure is formed on an oxide film, and in electrical contact with oneof the plurality of electrodes, formed as a raised electrode.
 14. Themethod of claim 1, wherein the beam structure is formed in an openposition and then placed in the closed position.
 15. A structure,comprising a beam structure comprising a first end hinged on a firstelectrode and in electrical contact with a second electrode, in itsnatural state when not actuated.
 16. The structure of claim 15, whereinthe beam structure and the second electrode are of different materials,and the second electrode is a cantilevered structure, extended about thebeam structure and above an end thereof
 17. A method in a computer-aideddesign system for generating a functional design model of amicromechanical switch, the method comprising: generating a functionalrepresentation of a beam structure comprising a first end hinged on afirst electrode and in electrical contact with a second electrode, inits natural state when not actuated.
 18. The method of claim 17, whereinthe functional design model comprises a netlist.
 19. The method of claim17, wherein the functional design model resides on storage medium as adata format used for the exchange of layout data of integrated circuits.20. The method of claim 17, wherein the functional design model residesin a programmable gate array.